Television receiver



July 28, 1953 Filed Sept. 6, 1950 P. C. JANSEN ET AL TELEVISION RECEIVER 2 Sheets-Sheet l \NVENTOR s Pia-ran czwaus JANsEN 5 Gaoaee Wcznwz' EN AGENT July 28, 1953 P. c. JANSEN ET AL TELEVISION RECEIVER 2 Sheets-Sheet 2 Filed Sept. 6, 1950 INVENTORS PiETER CORNELIS JANSEN GEORGE WEEHUIZEN Patented July 28, 1953 caries I TELEVISION RECEIVER Pieter CornelisJansen and. George Weehuizcn, Eindko'v-en, Netherlands, assignors to Hartford l'lational Banlc and Trust Company; Hartford,

Gonna. as trustee Appli'cafionsentemher 6, 195a,, sum no. 183,426

I'nlihance September- 21', I949 3- Claim (Cl. 14103 -3683 The invention relates generally to television. receivers comprising a cathode ray tube, andmore particularly to those receivers wherein the screen of the cathodeway tube constitutes the image surface of a Schmidt: optical system.

Generally speaking, such optical: systems: comprisea spherical mirror arranged opposite the aforesaid screen of the tubeand anelement for spherical aberration correction. The latter usually comprises a thin plate having one or, two non-spherical surfacesi The correction element which maybe comprised of a meniscus lens, cons centrates the light radiated by the screen of the tube into a beam. It is known to improve the contrast eztfect. of the image formed. by eliminating the central part of the mirror or by render-- ing it inactive in some other manner such as by" shielding, for example, but this measure results in a marked. loss of thelight. which ultimately impinges on. the viewing screen. Accordingly, effortswillordinarily be made to minimize the inactive central partof the mirror.

The invention is based "on recognition of the fact that.v the light radiated the screen or the. tube to the central part of the mirror allows. the projection of a second and eqrnval'ent image with the use ota second optical system. Thus, accordance with the invention, there is arranged in the central aperture of the spherical mirror of a Schmidt system, an optical system adapted to project a second image which is equivalent to that originally projected by the said Schmidt system.

The phrase in the central aperture of the mirror does not imply by any means that this system cannot project from either of the surfaces of the mirror, that is to say cannot be displaced axially of the mirror, but the portion of light reaching the aperture must be utilized to the utmost by the second system. The two images may be projected, for example, onto two screens parallel to each other and arranged on either side of the apparatus but the two pro-,

jection directions are preferably at right angles to each other.

The first system for projection onto two screens parallel to each other, as noted just above, may be a conventional Schmidt system in which all the elements comprising the same are located in the straight line of the optical axis thereof with the tube screen located in the focal plane of the spherical mirror and the correcting ele- I ment beyond. The second system may be a mirror-is provided with a small aperture. in.

such known constructions, a second optical sysw tem is arranged to control the image produced on the screen of the tube. This second system allows the passage of a very" small: portion. ofthe total fight supply from the screen of the tuba The present invention is not concerned with devices, wherein the images not; equivalent. In: order that the invention be more clear- 1y understood and readily carried into. effect, it. wilinow be described reference: to the accompanying two fissures of the drawings, which like parts are designated by the: same refieremzenumerals and in which:

Fig. 1 shows diagrammatically-a horizontal: sectiz'onal -view or the optical partof a television, re ceiver, accordance with one. embodiment of present invention, which the images are pro-- jiected onto two. paralielpl anea. s

Fig. 2 is a similar sectional view of .a' receiver, employing another preferred embodiment of the invention, in which the images are projected onto two planes at right angles to each other.

The receiver shown in Figure 1, and which allows projecting an image onto two parallel screens facing one another, comprises a cathoderay tube I, of which the screen 2 is arranged approximately at the focal plane of the spherical mirror 3. The beam reflected by this mirror passes through a correction element 4 comprising a thin plate having a non-spherical surface. The image is thus projected onto a screen 5 (shown close to element 4 due to lack of space). Accordingly, the rays [5 and I5 are shown in dotted lines beyond the element 4.

The mirror 3 is provided with an aperture, in which is arranged a second optical system, which is represented diagrammatically by a lens 9. This lens projects the light onto a screen I0 (again shown close to the remainder of the device due to lack of space).

In order that the images produced on the two screens should be equivalent, the quantities of light reaching the two systems must be of the same order of magnitude. This is accomplished by the suitable choice of the diameters and powers of the Schmidt system (mirror 3, element A), on

the one hand, and the lens 9 on the other. When I choosing the diameters of the mirror 3 and of the lens 9, allowance must, of course be made for the losses of light in the two optical systems which are due inter alia to absorption and refiection.

The device shown in Fig. 2 comprises in addilong wall I3 may be arranged against a wall of a room, for example. The spectators will then be arranged in a semi-circle in front of the receiver. The screens 5 and It may be shielded by rims H, for example, so that the light emanating from one screen does not interfere with the spectators in front of the other screen.

What we claim is:

1. A television reiceiver comprising a Schmidt optical system, and a cathode-ray tube; said Schmidt optical system comprising a spherical mirror and a correcting element, said cathoderay tube comprising a screen positioned in the image surface of said spherical mirror, said spherical mirror having the central part thereof inactive, a second optical system located in the zone of said inactive central part of said spherical mirror and adapted to project an image equivalent to that projected by said Schmidt optical system, and means for projecting the image produced by said Schmidt optical system at substantially right angles to the image produced by said second optical system.

2. A television receiver comprising a Schmidt optical system and a cathode-ray tube; said Schmidt optical system comprising avspherical mirror and a correcting element, said cathode-ray tube comprising a screen positioned in the image surface of said spherical mirror, said spherical mirror having the central part thereof inactive,

a second optical system located in the zone of said inactive central part of said spherical mirror and adapted to project an image equivalent to that projected by said Schmidt optical system, a first screen located on the optical "axis of said second optical system and adapted toreceive said image projected thereby, means for projecting the image produced by said Schmidt optical system at substantially right angles to the image produced by said second optical system, and a second screen located on the optical axis of said Schmidt optical system and adapted to receive said image projected thereby.

3. A television receiver comprising a cabinet, a Schmidt optical system and a cathode-ray tube housed in said cabinet; said Schmidt optical system comprising a spherical mirror and a correcting'element, said cathode-ray tube comprising a screen positioned in the image surface of said spherical mirror, said spherical mirror having the central part thereof inactive, a second optical system located in the zone of said inactive central part of said spherical mirror and adapted to project an image equivalent to that projected by said Schmidt optical system, a first screen mounted on said cabinet and located on the optical axis of said second optical system and adapted to receive said image projected thereby, means for projecting the image produced by .said Schmidt optical system at substantially right angles to the image produced by said second optical system, and a second screen mounted on said cabinet and located on the, optical axis of said Schmidt optical system and adapted to receive said image projected thereby, said first andsecand screens being positioned at substantially right angles to each other. I

PIETER CORNELIS JANSEN. GEORGE WEEHUIZEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date I 2,476,124 Alphen July 12, 1949 2,489,835 Traub Nov. 29, 1949 2,490,740 Nicoll Dec. 6, 1949 2,508,764 Miller May 23, 1950 

